1. Field of the Invention
The present invention concerns an electromagnetic coil device used, for example, in a torque detector. More specifically the present invention relates to an electromagnetic coil device, which comprises a coil assembly including a bobbin made of a synthetic resin and coils wound around the bobbin, a housing made of a synthetic resin and integrally having a coupler for covering the coil assembly, an electric circuit contained in the housing, and a plurality of bus-bars each having one end arranged in the coupler and the other end connected to the electric circuit for insertion molded to the housing.
1. Description of the Prior Art
Most of existent electromagnetic coil devices of the above-mentioned type have electric circuits located outside the housings and, accordingly, are not compact in the constitution. Therefore, it may be considered to contain the electric circuits in the housing of the device. For this purpose, however, a plurality of bus-bars which connect a coupler formed on the housing with the electric circuits have to be insertion molded at accurate locations during molding process for the housing, which may possibly cause misalignment.
Further, when connection terminals as a portion of the bus-bars are connected to the board of the electric circuit, for example, by soldering, the connection terminals may possibly be detached from the circuit board because of thermal expansion and shrinkage of the terminals during heat treatment. In a customary countermeasure, the connection terminals are previously bent to absorb expansion and shrinkage in the bent portion. However, when the connection terminals are formed from the portion of bus-bars joined by insertion-molding to the housing, they must be bent after molding of the housing, because of structural restriction of the housing molding die, which complicates the bending operation for the connection of the terminals or requires a bending jig of a special structure.
The present invention has been made in view of the situations described above and intends to provide an electromagnetic coil device in which a plurality of bus-bars can be insertion molded to a housing while preventing misalignment during molding of the housing.
The present invention also intends to provide a structure for connecting terminals to a circuit board, for example, in an electromagnetic coil device which can easily bend connection terminals by a simple jig.
The foregoing object can be attained in accordance with the first feature of the present invention by an electromagnetic coil device, comprising:
a coil assembly including a bobbin made of a synthetic resin and coils wound around the bobbin;
a housing made of a synthetic resin and integrally having a coupler for covering the coil assembly;
an electric circuit contained in the housing; and
a plurality of bus-bars, each having one end arranged in the coupler and the other end connected to the electric circuit for insertion molded to the housing, in which
a bus-bar assembly comprises the plurality of bus-bars including bus-bars having caulking portions which can be engaged by caulking with the bobbin and a cover made of a synthetic-resin which partly covers the bus-bars and is formed in such a shape as capable of abutting against the outer periphery of the coil assembly; and
the housing covers the coil assembly and the bus-bar assembly which is temporarily secured to the coil assembly by abutting the cover against the outer periphery of the coil assembly and by engaging by caulking the caulking portions with the bobbin.
According to the first feature of the present invention, positional misalignment of the bus-bars caused by the pressure of the molten resin during molding of the housing can be prevented by temporarily securing the bus-bar assembly to the coil assembly during molding of the housing and the plurality of bus-bars can be insertion molded under accurate positioning to the housing.
Further, in a preferred embodiment, the cover for the bus-bar assembly has flow control portions formed to inhibit flow of a molten resin from flowing into a gap between the bus-bar assembly and the coil assembly and guide the flow of the molten resin to the outer periphery of the bus-bar assembly during molding of the housing.
In this preferred embodiment, misalignment of the bus-bar assembly can be prevented more reliably by inhibiting the pressure of the molten resin from exerting on the bus-bar assembly in direction of causing the bus-bar assembly to recede from the coil assembly and deformation in the bus-bar assembly by the pressure of molten resin can also be prevented.
Another object can be attained in accordance with the second feature of the present invention by a structure for use in an electromagnetic coil device, comprising a coil assembly, a housing made of a synthetic resin covering the coil assembly, an electric circuit board contained in the housing and bus-bars insertion molded to the housing, and adapted for connecting connection terminals to the circuit board, the connection terminals being formed from a portion of the bus-bars made of a conductive metal insertion molded to the housing made of a synthetic resin and being protruded from the housing, in which
terminal bending pedestals adjacent to the respective connection terminals are formed to the housing upon molding of the housing; and
the connection terminals bent by pressing the connection terminals against the bending pedestals are connected to the circuit board.
According to this second feature of the present invention, the connection terminals as the portion of the bus-bars insertion molded to the housing can be bent after molding the housing by being pressed against the bending pedestal. Further, since such a jig used for bending can be of a simple shape the connection terminal can be bent easily by using a simple jig.
Further, in a preferred embodiment, a notch is previously formed to each of the connection terminals at a location where the terminal is bent by being pressed against the bending pedestal.
In this preferred embodiment, the connection terminal can be bent more easily.